1. Field of the Invention
My present invention relates to operators for sliding gates, and more particularly to operators for heavy duty sliding gates such as those used to control the access of vehicles to parking areas and the like.
2. Description of the Prior Art
Operators for heavy duty sliding gates are well-known in the prior art. Such prior art gate operators typically comprise a weatherproof metal cabinet containing an electrical drive motor for driving an associated sliding gate between its limits of travel.
Also typically contained in the cabinet of such a prior art gate operator is a shaft speed reducer which is coupled between the output shaft of the drive motor and a stub shaft which carries a gate drive sprocket, and which is journalled in a bearing mounted in an opening in a wall of the cabinet. The gate drive sprocket is itself located immediately outside the cabinet wall.
In a typical prior art sliding gate operator installation the cabinet is located closely adjacent the gate, which is provided with a drive chain extending from end to end thereof and fastened to the gate at its ends. The gate drive chain is typically engaged with the gate drive sprocket and also engaged with two cooperating idler sprockets, which are themselves mounted on shafts which are journalled in bearings mounted in openings in the same wall of the cabinet. Such a prior art gate operator cabinet also typically contained an electronic control unit which serves to control the operation of the associated gate drive motor in response to suitable signals provided by, e.g., remote control radio transmitters, keys inserted in suitable locks carried by the cabinet, etc.
Power for operating the gate drive motor and exciting the components of the electronic control unit is typically supplied by means of a power connection which passes through a suitable opening in the cabinet wall.
Many of such prior art gate operators are characterized by certain deficiencies or disadvantages which render them less than fully effective to serve their intended purpose.
For example, when the operators of certain prior art sliding gate installations are de-energized (e.g., due to a power failure) the gates of those installations can be manually forced open by persons unauthorized to do so.
Further, the gates of certain prior art sliding gate installations are effectively locked in the open position (or sometimes the closed position) when an associated remote control transmitter with its operating switch inadvertently continuously depressed is located in the vicinity of the gate installation.
Yet further, certain prior art sliding gate operators are not provided with gate movement brakes which operate sufficiently rapidly to prevent property damage or personal injury when the presence of a vehicle or person in the path of motion of the gate is detected by an associated gate blockage detector, such as the gate blockage detector of my U.S. Pat. No 4,335,339.
(The term "prior art" as used herein or in any statement made by or on behalf of applicant means only that any document or thing referred to as prior art bears, directly or inferentially, a date which is earlier than the effective filing date hereof.)